1. Field of the Invention
The present invention relates to electronic testing equipment and methods, and more particularly to testing equipment to be used for diagnosing electronic automotive system faults.
2. Description of the Prior Art
With increasing use and complexity of electronics in automotive applications, expedient and accurate diagnosis of electronic automotive electronic system's faults has become difficult, and in some cases impossible. Traditionally, the training of automotive repair personnel emphasizes the understanding of mechanical technology, making the `troubleshooting` of electronic automotive systems a somewhat daunting and alien prospect to a traditionally trained automotive repair technician. Also, because of the constant and rapid evolution of automotive electronics, knowledge and equipment used to diagnose electronic automotive systems quickly become obsolete making the task of updating testing and diagnostic equipment and retraining personnel difficult and expensive. Further, due to the interactions between components in electronic automotive systems, it is often difficult to `pinpoint` the problem to a specific electronic components. An ignition computer unit, for example, may appear to malfunction when, in fact, a broken sensor is supplying the computer with false information. Often, because of the above-mentioned problems, the repair technician resorts to the slow, costly plan of almost arbitrarily replacing components and observing the effect of the replacement on the automobile in an attempt to isolate the malfunctioning component. This method, in addition to costliness in time and money, has proven to be inaccurate as it has been empirically found that a significant portion of those automotive electronic components (especially engine control computers) submitted for repair are, in fact, functionally sound with the original problem being elsewhere.
Various electronic systems have been devised to aid in the diagnosis of automotive electronic faults. These testing/diagnostic systems, however, suffer from a number of drawbacks which seriously diminish their effectiveness. Many of these testing/diagnostic systems test automotive electronics through a purpose-built diagnosis data interface installed in the electronic automotive system. The problem with this, of course, is that the diagnostic data interface may, itself, be malfunctioning, may be involved in the malfunction, or may be fooled by erroneous data received from components peripheral to the electronic automotive system under test.
Other testing/diagnostic systems bypass the purpose-built diagnostic data interface and directly read the functional outputs (a functional output being those outputs used to control peripheral components that have a direct effect on the performance of the automobile) of the electronic automotive system being tested. Although this method prevents misdiagnosis due to malfunction of the diagnostic interface, misdiagnosis is possible (and, as practical experience has proven, is common) because the electronic automotive system under test is reacting appropriately to erroneous information from peripheral components.
Also, a fault in the electronic automotive system may be intermittent or be particular to certain operating conditions and appear intermittently. Many of the known electronic testing/diagnostic systems are designed to work in the automotive repair shop (where operating conditions rarely change a significant amount) and, therefore, cannot test the automotive electronics under a variety of operating conditions This "static" or steady-state, testing of the electronic automotive system will tend to entirely miss condition-dependent faults in the automobile's electronics. Other testing/diagnostic systems, in an attempt to facilitate the diagnosis of condition-dependant faults, are physically small and are designed to be used while the car is in motion and actually experiencing varying driving conditions. Although this method seems to be an improvement over "static" testing, it leaves much to be desired. This "driving" test method is inconvenient in that the automotive repair technician has to actually drive the automobile until the fault appears, wasting time and fuel. Also, it may be difficult, undesirable, or dangerous to expose the automobile to extreme operating conditions in order to find an electronic fault with the "driving" test method.
As has been discussed, currently used electronic testing/diagnostic systems tend to be inaccurate and inconvenient to use and often wind up unused in the corner of the repair garage.